1. Field of the Invention
The invention relates to a light emitting device, more particularly, to a light emitting device utilizing a light-emitting diode as a light source.
2. Description of Related Art
With development of optoelectronic techniques, light emitting mechanism of light emitting devices has evolved from thermoluminescence into electroluminescence (EL). Light emitting devices with electroluminescence mechanism usually emit light in different colors by using a phosphor, which is a common method used for converting a wavelength of the light emitted by the light emitting device.
In regard to an LED illuminating device, a phosphor-converted cover is usually disposed above an LED light source module so as to emit light in different colors. A white-light conversion may then begin once the light emitted from the LED light source module is emitted to the phosphor-converted cover. However, heat generated by the LED light source module and heat generated during the white-light conversion may both be accumulated on the phosphor-converted cover, causing temperature of the phosphor-converted cover to rise. Since the phosphor-converted cover is composed by a phosphor and a high-molecular material or a glass, an effect of thermal quenching of luminescence may occur when the temperature of the phosphor-converted cover rises. As a result, efficiency of a phosphor-conversion may be reduced thereby generating a color washout phenomenon.